Novel chemical compounds of the general formula K+A-, in which K+ is a 5- or 6- membered heterocyclic ring having 1-3 hetereo atoms, which can be independently N, S, or 0; with the proviso that at least one of the hetereo atoms must be a quaternized nitrogen atom having a -R'CN substituent, wherein R' is alkyl (C1 to C12); the heterocyclic ring having up to 4 or 5 substituents independently chosen from the moieties: (i) H; (ii) halogen or (iii) alkyl (C1 to C12) , which is unsubstituted or partially or fully substituted by further groups, preferably F, Cl, N(CnF(2n+1-x)Hx)2, O(CnF(2n+1-x)Hx), S02(CnF(2n+1-x)Hx)2 or CnF(2n+1-x)Hx where 1